PCI: rcar-host: Add support for optional regulators

The KingFisher board has regulators for miniPCIe, so enable these
optional regulators using devm. devm will automatically disable them
when the driver releases the device. Order variables in reverse-xmas
while we are here.

[kwilczynski: update style to match rest of the code]
Link: https://lore.kernel.org/linux-pci/20231105092908.3792-3-wsa+renesas@sang-engineering.com
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Manivannan Sadhasivam <mani@kernel.org>